How deep should I let the snow on the roof get before I remove it?

Answer 1

Here is some info about snow loading on agricultural buildings:
"Many roofs for livestock barns and machine sheds are designed for a total load of 25 to 30 lb per square foot. Roofs should be able to handle this load if the building was properly designed by a registered professional engineer and constructed by a qualified builder who followed the design.
How much does snow weigh? A one inch layer of water or ice weighs approximately five lb per square foot. A roof designed for a 20 lb per square foot snow load could theoretically hold up to four inches of ice. How much snow is that? Meteorologists estimate that about 12 inches of snow is equivalent to one inch of water, which means a roof should hold up to four feet of snow. Wet and packed snow weighs more, so a roof with a load of wet or packed snow might only be able to hold up to three feet of snow. A roof might be able to support the maximum snow load for several days or a few weeks, but probably no more than 30 days because wood can fail due to fatigue under prolonged loading.
What is a safe amount of snow to have on your roof over an extended period of time? A good estimate would be about half of the 20 lb per square foot design load, or about two feet of snow, or approximately one inch of ice and one foot of snow."
Also, I think a lot depends on the pitch of your roof, as well as the construction. I also included a reference to snow loading from Juneau Alaska.

Answer 2

It would depend on a couple of factors. First the pitch of your roof determines the amount of download that it can support ( steeper is stronger as it transfers the load down and to the walls and floor system, whereas softer pitch keeps the load on the rafters) As well as what material the roof is framed with (trusses, 2x8, 2x10, etc..) There is also the wetness of the snow, if it's very dry it will be lighter, and heavier if wet. You'd better consult someone who knows about such things in your area.

Answer 3

Depends on how strong your roof is and what it is sheathed with. If it is plywood and 2x6 then not more than a foot and a half. If it is plank and 2x10 truss then it will hold more than twice that. Running a space heater in your attic during the day would help bleed off the snow, but you have to stay with it or you risk having a fire.

Answer 4

You should not have a problem if its not over 3 feet on a flat roof but you must make sure that your drain box is kept free of ice and your spout is free. If you can clear drain area and put a bit of ice melt around box before it re-freezes when the temp. drops at night.